S. Fazekas De St. Groth

Nasal mucus and influenza viruses. I. The haemagglutinin inhibitor in nasal secretions.

In the course of studies on experimental influenza in mice it was observed that the haemagglutinin inhibitor, normally present in bronchial washings, disappeared in the early stages of infection (Fazekas de St Groth, 1950a). The absence of the inhibitor showed good correlation with the presence of active virus in the respiratory tract, and since the virus is capable in vitro of enzymically destroying the inhibitory capacity of bronchial mucus, it was assumed that the same reaction took place in vivo. Consequently, the drop in inhibitory titre can be regarded as a measure of virus activity in the air passages, and hence a diagnostic sign of influenza infection. Indeed, it has been shown (Fazekas de St Groth, 19506) that the experimental disease of mice can be recognized as readily by this criterion as either by the recovery of virus from the lung tissue during the disease, or by the evaluation of macroscopic lesions seven days after infection, or, retrospectively, by the demonstration in the serum of specific antibodies in the stage of convalescence. These findings prompted an attempt to develop a similar method for the diagnosis of human influenza, and the 1950 epidemic offered an opportunity to test the proposition. The work consisted of two, essentially independent, phases. First, the characterization of normal human respiratory mucus as regards its reactions with influenza viruses—the subject of the present communication. Secondly, observations made on established cases of influenza during the epidemic— to be reported in the accompanying paper. A preliminary note, containing a summary of the results, has appeared (Fazekas de St Groth, 1951).